1. Field of the Invention
The present invention relates to solar power production, and more particularly, to solar receiver panels for use in solar boilers.
2. Description of Related Art
Solar power generation has been considered a viable source to help provide for energy needs in a time of increasing consciousness of the environmental aspects of power production. Solar energy production relies mainly on the ability to collect and convert energy freely available from the sun and can be produced with very little impact on the environment. Solar power can be utilized without creating nuclear waste as in nuclear power production, and without producing pollutant emissions including greenhouse gases as in fossil fuel power production. Solar power production is independent of fluctuating fuel costs and does not consume non-renewable resources.
Solar power generators generally employ fields of controlled mirrors, called heliostats, to gather and concentrate sunlight on a receiver to provide a heat source for power production. A solar receiver typically takes the form of a panel of tubes conveying a working fluid therethrough. Previous solar generators have used working fluids such as molten salt because it has the ability to store energy, allowing power generation when there is no solar radiation. The heated working fluids are typically conveyed to a heat exchanger where they release heat into a second working fluid such as air, water, or steam. Power is generated by driving heated air or steam through a turbine that drives an electrical generator.
More recently, it has been determined that solar power production can be increased and simplified by using water/steam as the only working fluid in a receiver that is a boiler. This can eliminate the need for an inefficient heat exchanger between two different working fluids. This development has lead to new challenges in handling the intense solar heat without damage to the system. One such challenge involves the fact that in order to maximize power output, heliostat fields are typically arranged to surround a central receiver tower so the boiler on the tower can receive solar energy from all around.
Typical boilers include two or more sections at different temperatures and pressures, such as a section of steam generator panels, a section of superheater panels, and a section of reheater panels, for example. Each section typically includes multiple receiver panels each having a series of tubes running from a common inlet header to a common outlet header. In high capacity solar boilers, there is typically a field of heliostats surrounding the boiler on all sides. Typical solar boilers are built to be generally circular so as to be able to collect sunlight from heliostats on all sides. Due to the round configuration, the headers of the panels constructed in the conventional manner tend to limit the proximity possible from panel to panel. This causes vertical gaps between the individual panels due to the slight angle between adjacent panels needed for the round configuration.
One approach to this problem is to stager the individual panels at different heights around the boiler so the headers do not interfere with each other. This allows the panels to be arranged more tightly together, without significant vertical gaps therebetween. However, if multiple boiler sections, e.g., a steam generator and a superheater, were arranged vertically in a stack, the staggered approach would increase the horizontal gap between the sections because of the extra space needed to stagger the headers. Still another approach is to bevel the headers of individual panels to reduce vertical gaps between the panels, but even this approach would leave a horizontal gap between stacked boiler sections where the headers are located. Gaps in the receiver area of a boiler constitute area where available sunlight from the heliostats is not captured. In typical solar boilers with horizontal gaps between vertically stacked sections, the gaps must be covered with a shielding panel which blocks concentrated sunlight from the heliostats. The blocked concentrated sunlight is thus not made available for power production.
While the known systems of solar power production have generally been considered satisfactory for their intended purposes, there has remained a need in the art for solar receivers that can improve the overall efficiency and capture more of the solar power made available by heliostats by reducing or eliminating gaps between receiver sections. There also has remained a need in the art for such solar receivers that are easy to make and use. The present invention provides a solution to these problems.